SEATTLE, May 31, 2007 /PRNewswire-FirstCall/ -- Vical
Incorporated today announced that a measles DNA vaccine formulated
with the company's Vaxfectin(TM) adjuvant elicited protective
levels of neutralizing antibodies in juvenile (1 - 2 year old)
nonhuman primates confirmed by complete protection following
challenge more than one year after vaccination, and sterilizing
immunity as evidenced by no clinical signs of disease and no
detectable virus after challenge. In a separate study, the same
vaccine elicited protective levels of neutralizing antibodies in
infant (6 - 10 weeks old) nonhuman primates with no vaccine-related
adverse events. The studies were conducted in collaboration with
Diane E. Griffin, M.D., Ph.D., Alfred and Jill Sommer Professor and
Chair of Molecular Microbiology and Immunology, Johns Hopkins
Bloomberg School of Public Health, under a grant from the Bill and
Melinda Gates Foundation.

"Sterilizing immunity is a rarely achieved ultimate goal in
vaccination," said Vijay B. Samant, Vical's President and Chief
Executive Officer. "The ability to provide such complete immunity
with no adverse events offers proof of concept for
Vaxfectin(TM)-formulated DNA vaccines. We look forward to continued
development of the measles vaccine program by our collaborators at
Johns Hopkins."

"We have tested a number of measles DNA vaccines, and the data
relating to Vical's Vaxfectin(TM)-formulated DNA vaccine showed
marked differences both in terms of disease resistance after
exposure and antibody levels over the other vaccines, without
significant side effects," said Dr. Griffin. "These data are
exciting because of the potential of providing safety and efficacy
suitable for infants and young children in the developing world,
and continued development could result in a major impact on global
measles disease and death rates."

The study in juvenile rhesus macaques tested the protective
efficacy of a bivalent DNA vaccine encoding measles hemagglutinin
and fusion glycoproteins. Vaccine was delivered by intradermal
needle-and-syringe injection of two 0.5 mg doses or by
intramuscular needle-and-syringe injection of two 1.0 mg doses at
four-week intervals. All vaccines were formulated with Vical's
patented Vaxfectin(TM) adjuvant. Neutralizing antibody levels
exceeded the accepted protection threshold prior to the second
injection at Week 4, peaked at Week 5, and remained well above the
accepted protection threshold for more than one year, with no
difference noted between routes of administration. Animals were
challenged by intratracheal inoculation at Week 55, resulting in
complete protection of all vaccinated animals against disease
symptoms. None of the vaccinated animals had detectable levels of
measles virus at any time point tested, in contrast to negative
control animals which all had detectable virus. Measles-specific
T-cell responses were also detected after vaccination. The vaccines
were well-tolerated in all animals.

The study in infant rhesus macaques tested only intradermal
needle-and- syringe delivery of vaccine at the same 0.5 mg dose
used in the juvenile animals. Neutralizing antibody levels exceeded
the accepted protection threshold prior to the second injection at
Week 4, peaked at Week 8, and remained above the accepted
protective level throughout the 20-week follow-up period. No
adverse events related to the vaccination were observed. Data were
presented by Adrian Vilalta, Ph.D., Vical's Senior Scientific
Manager of Immunogen Discovery, at the annual meeting of the
American Society of Gene Therapy (Seattle, May 30 - June 3).

About Measles

Routine vaccination with a live attenuated measles vaccine has
largely eliminated the disease among children in most developed
countries, however, it remains among the top ten infectious disease
causes of deaths among young children worldwide because of poor
vaccine acceptance in some countries, poor vaccine availability in
others, and lack of effectiveness in young infants. Measles causes
approximately one of every five deaths from vaccine-preventable
diseases in children under age five. The disease is particularly
prevalent in infants less than one year old in developing
countries, and is most severe among those who are malnourished.

About Vical

Vical researches and develops biopharmaceutical products based
on its patented DNA delivery technologies for the prevention and
treatment of serious or life-threatening diseases. Potential
applications of the company's DNA delivery technology include DNA
vaccines for infectious diseases or cancer, in which the expressed
protein is an immunogen; cancer immunotherapeutics, in which the
expressed protein is an immune system stimulant; and cardiovascular
therapies, in which the expressed protein is an angiogenic growth
factor. The company is developing certain infectious disease
vaccines and cancer therapeutics internally. In addition, the
company collaborates with major pharmaceutical companies and
biotechnology companies that give it access to complementary
technologies or greater resources. These strategic partnerships
provide the company with mutually beneficial opportunities to
expand its product pipeline and address significant unmet medical
needs. Additional information on Vical is available at www.vical.com.

This press release contains forward-looking statements subject
to risks and uncertainties that could cause actual results to
differ materially from those projected, including: whether Vical or
others will continue evaluation of the Vaxfectin(TM)-formulated
measles DNA vaccine; whether the vaccine will be effective in
protecting juvenile or infant humans against measles infection or
disease; whether the measles vaccine or any other product
candidates will be shown to be safe and effective in clinical
trials; the timing, nature and cost of clinical trials; the
availability of future funding to support the cost of continued
development; whether Vical or its collaborative partners will seek
or gain approval to market the measles vaccine or any other product
candidates; whether Vical or its collaborative partners will
succeed in marketing the measles vaccine or any other product
candidates; whether the company's issued patents will be challenged
and whether such challenges will have an adverse effect on the
scope of the patents; whether the company will enforce its issued
patents or will be successful in any enforcement efforts; and
additional risks set forth in the company's filings with the
Securities and Exchange Commission. These forward-looking
statements represent the company's judgment as of the date of this
release. The company disclaims, however, any intent or obligation
to update these forward-looking statements.

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